Typically, doors are provided with a standard backset which defines the distance between the rotational axis of the operating knob and the edge of the door from which the latch bolt extends. Most modern doors are provided with a backset of 23/4" while older doors and a minority of modern doors have a backset of 23/8". Thus, if the door hardware needs to be replaced, the user must locate a door latch which has the identical backset. Accordingly, hardware suppliers must stock latches for both types of backsets.
Adjustable backset door latches have been developed which utilize various mechanisms to vary the distance between the door edge and the rotational axis of the latch knob. However, the available space within the door is limited and therefore the length of the latch must correspond to the door configuration. Several prior known latches with adjustable backsets employ telescopingly extendable mechanisms which require additional preparation of the door. Still other designs comprise complicated mechanisms which can not be cost-effectively manufactured or have an unacceptable failure rate.